1. Field of the Invention
The present invention generally relates to the protection against tampering of security features incorporated in chip cards.
2. Background Art
A chip card comprises a card body and a chip module which is embedded in the card body and incorporates an integrated circuit (IC).
In addition to the embedded IC, so-called “security features” are often present on the surface of the card body. As a matter of fact, since smart cards are often used for authorising certain operations or to personally identify the holder of the card, it is necessary to include in the card some physical features that may be characterised on visual inspection, in contrast to authentication algorithms which rely on the exchange of signals with the microprocessor of the IC.
There has been proposed a number of security features, such as a photograph of the holder of the card, holograms, hologram-like features such as multiple laser images (MLI), laser engraving of individual data such as name and card number, etc. These features are created directly on the card body at the manufacturing stage, or maybe added at a later stage in the course of the personalization step of the blank card.
A problem nevertheless remains in ensuring integrity and security of the card. Though it is generally difficult to modify features as holograms, laser engraving, etc. without blatant alteration of the card, there exists some simple frauds consisting e.g. in peeling as a whole a layer of the card to replace printed or engraved information, still keeping unchanged the other layers of the cards and the chip module. Photographs printed on a card, like on driving licenses, passport, etc. are usually the first targets of such physical attacks.
Another attack consists in keeping the card body with all its security features as such, but removing the chip module and replacing it by a counterfeited module or a module taken from another card.
In order to make such physical attacks more difficult or render them more apparent in case of alteration of the card, multiple, different security features are incorporated in a single card and/or more and more sophisticated security features are used.
However, this makes the manufacturing process more complex and more expensive, while remaining vulnerable to some kinds of physical attacks such as exchanging the IC or peeling as a whole the layer incorporating the different security features. Thus the security features proposed so far, despite their sophistication, are not really tamper-proof and are still open to some kind of physical attacks.